Protesters, including college students, fast-food restaurant employees and other workers, display placards as they march April 14, in Boston. Organizers of the event are calling for the nation's lowest paid workers to earn at least $15 per hour.

Washington and Boston — Pocketbook concerns are meeting up with social justice activism.

Protests on Wednesday aimed at raising pay for low-wage workers reached 230 cities. A key focus of the rallies has been fast-food restaurants, which pay some of the lowest wages in the United States. The slogan “Fight for $15” urges an ambitious goal: $15 an hour even at a McDonald’s.

But the activism has gone beyond restaurants, speaking to concerns that experts say are widespread. The aim now is to help a wide range of financially stretched workers, from those in health care to retail employees.

A few years ago, the Occupy Wall Street movement started to focus national attention on the economic power of “the 1 percent.” In the more recent wave of protests, workers are stepping out to highlight issues that affect not only them, but also a wide swath of Americans. And they’re sharing their stories to show just what’s at stake.

The protesters now have a concrete goal to rally behind: higher wages. And despite signs of improvement in the job market, they are animated by deep concerns about widening income gaps between ordinary workers and the wealthy – and the sense that ladders of opportunity are disappearing for too many low-income Americans.

“[The wage push] is one element of what seems to be a larger shift in the culture, in which I think people have become much more attuned to the level of inequality,” and the question of whether income gaps are at an unsustainable peak, says Nancy MacLean, a historian of social movements at Duke University in Durham, N.C.

“You see these discussions starting to happen in church congregations,” on campuses, and even within institutions like the International Monetary Fund, not just in labor halls, she says.

The labor movement has been learning to tap into these concerns and anxieties, allying with union and nonunion workers alike. At a time when overall union membership in the US continues to decline, the protests may offer a template for new success.

Dawn O’Neal, a day-care worker who protested in Atlanta Wednesday, first heard about the wage rallies through friends she knew from the Black Lives Matter movement.

“First they were talking about fast-food workers, but then they began talking about child-care workers, too,” Ms. O’Neal says. “I realized that was right up my alley, so I jumped in feet first.”

At the day-care center, O’Neal makes $8.50 an hour. That, coupled with hours that can fall short of her hoped-for 40 hours per week, makes it hard to pay her bills. “You expect your check to look like this, but then they send you home,” she says.

“I feel like a hamster in a cage, not getting anywhere. We get up and go to work and come home, and we’re getting nowhere. Nothing is being saved,” she says.

That sentiment resonates with many Americans who make more than her hourly rate.

For US workers on average, compensation per hour has flatlined relative to inflation since the end of the recession in 2009, according to government data tracked by researchers at the Federal Reserve Bank of Cleveland. That’s a contrast to the upward trend seen after the recessions that ended in 1982, 1991, and 2001.

Wages are a vital barometer of the economy’s health, but other issues related to work register, too. Despite an improving job market, many Americans remain worried about secure employment, or have jobs that don’t provide health benefits or paid time off.

Families that consider themselves middle class are struggling to pay off student debt, save for emergencies, or prepare for retirement. Many worry that their children won’t have the upward mobility that their parents did.

Meanwhile, top earners have generally prospered and pulled ahead.

All this doesn’t mean Americans are about to stage a rebellion against the wealthy elite. But polls by the Pew Research Center suggest a strong public concern about inequality and fairness in the economy.

For Judith Mendez, a $10-an-hour airport worker in Boston, the wage movement is a ray of hope.

“If everyone gets together and works together, I think we can accomplish something,” says Ms. Mendez, a Honduran immigrant who was protesting in Boston on Tuesday.

Her salary was enough to assist her family when her husband was also working in the US. But last year he was deported, and she and their three teenagers were forced to move from an apartment into a $550-per-month rented bedroom.

A curtain separates one section of the small room so her son can have some privacy, she says in an interview conducted in Spanish.

“Sometimes my children ask me when we can move out of here and into a regular apartment, and I just have to say, ‘We can’t, baby,’ ” Mendez says.

In “real” terms (inflation-adjusted), the federal minimum wage of $7.25 an hour is well below its 1968 peak – when its purchasing power equaled about $10.79 an hour today.

The federal minimum has also often been lower than $7.25 in real terms, so today’s level is not a low point.

Thanks in part to the push from labor, many states and cities have enacted their own higher minimums.

Still, a sign of stress for working families is that many rely on food stamps or other public assistance to help cover basic costs.

Michael Thompson of Washington, D.C., is a home health-care worker who has not gotten the $14.95-an-hour pay he says he was initially promised. He’s helped by $60 a month in SNAP funds for food, even as he scrambles to cover $1,435 per month in apartment rent (shared with a roommate) and $9 a day for transportation to and from work.

“If I’m worried about how I’m going to eat, how can I take care of a client?” asks Mr. Thompson, who was preparing to march on Wednesday when he was interviewed by phone.

“What the $15 would do is it would bring just the top of my head to the surface, it would bring me there. Right now I’m underwater,” he says.